Gladiolus corm losses due to F. oxysporum f. sp. gladioli were severe on 2 farms where benomyl had been applied as a corm dip during a 30-month period. Isolates of the pathogen from corms on those farms tolerated over 200 times more benomyl than isolates from corms not treated with benomyl. Benomyl-tolerant strains also tolerated thiadiazole and thiophanate-methyl and were as pathogenic to corms as non-tolerant strains.